src/share/classes/java/lang/Integer.java

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rev 9925 : 8041972: Add improved parse/format methods for Long/Integer
Contributed-by: redestad

@@ -525,18 +525,43 @@
      *             specified radix.
      * @exception  NumberFormatException if the {@code String}
      *             does not contain a parsable {@code int}.
      */
     public static int parseInt(String s, int radix)
-                throws NumberFormatException
-    {
+                throws NumberFormatException {
+        return parseInt(s, radix, 0);
+    }
+
+    /**
+     * Extend upon Integer.parseInt(String, int) by providing a start offset to enable parsing
+     * substrings without creating intermediary objects
+     * @see java.lang.Integer#parseInt(String, int)
+     *
+     * @param start the start position in s to parse from, inclusive
+     */
+    static int parseInt(CharSequence s, int radix, int start)
+            throws NumberFormatException {
+        if (s == null) {
+            throw new NumberFormatException("null");
+        }
+        return parseInt(s, radix, start, s.length());
+    }
+
+    /**
+     * Extend upon Integer.parseInt(String, int) by providing a start and end offset to enable parsing
+     * substrings without creating intermediary objects
+     * @see java.lang.Integer#parseInt(String, int)
+     * @param start the start position in s to parse from, inclusive
+     * @param end the end position in s to parse to, exclusive
+     */
+    static int parseInt(CharSequence s, int radix, int start, int end)
+            throws NumberFormatException {
         /*
          * WARNING: This method may be invoked early during VM initialization
          * before IntegerCache is initialized. Care must be taken to not use
          * the valueOf method.
          */
-
         if (s == null) {
             throw new NumberFormatException("null");
         }
 
         if (radix < Character.MIN_RADIX) {

@@ -547,49 +572,64 @@
         if (radix > Character.MAX_RADIX) {
             throw new NumberFormatException("radix " + radix +
                                             " greater than Character.MAX_RADIX");
         }
 
+        if (start < 0 || start > end) {
+            throw new NumberFormatException("start position out of bounds");
+        }
+
+        if (start == end) {
+            throw NumberFormatException.forInputString("");
+        }
+
+        if (end > s.length()) {
+            throw new NumberFormatException("end position out of bounds");
+        }
+
         int result = 0;
         boolean negative = false;
-        int i = 0, len = s.length();
+        int i = start;
         int limit = -Integer.MAX_VALUE;
         int multmin;
         int digit;
 
-        if (len > 0) {
-            char firstChar = s.charAt(0);
+        char firstChar = s.charAt(start);
             if (firstChar < '0') { // Possible leading "+" or "-"
                 if (firstChar == '-') {
                     negative = true;
                     limit = Integer.MIN_VALUE;
-                } else if (firstChar != '+')
-                    throw NumberFormatException.forInputString(s);
+            } else if (firstChar != '+') {
+                throw NumberFormatException.forInputString(
+                        s.subSequence(start, end).toString());
+            }
 
-                if (len == 1) // Cannot have lone "+" or "-"
-                    throw NumberFormatException.forInputString(s);
+            if (end == start + 1) { // Cannot have lone "+" or "-"
+                throw NumberFormatException.forInputString(
+                        s.subSequence(start, end).toString());
+            }
                 i++;
             }
             multmin = limit / radix;
-            while (i < len) {
+        while (i < end) {
                 // Accumulating negatively avoids surprises near MAX_VALUE
-                digit = Character.digit(s.charAt(i++),radix);
+            digit = Character.digit(s.charAt(i++), radix);
                 if (digit < 0) {
-                    throw NumberFormatException.forInputString(s);
+                throw NumberFormatException.forInputString(
+                        s.subSequence(start, end).toString());
                 }
                 if (result < multmin) {
-                    throw NumberFormatException.forInputString(s);
+                throw NumberFormatException.forInputString(
+                        s.subSequence(start, end).toString());
                 }
                 result *= radix;
                 if (result < limit + digit) {
-                    throw NumberFormatException.forInputString(s);
+                throw NumberFormatException.forInputString(
+                        s.subSequence(start, end).toString());
                 }
                 result -= digit;
             }
-        } else {
-            throw NumberFormatException.forInputString(s);
-        }
         return negative ? result : -result;
     }
 
     /**
      * Parses the string argument as a signed decimal integer. The

@@ -655,38 +695,63 @@
      *             does not contain a parsable {@code int}.
      * @since 1.8
      */
     public static int parseUnsignedInt(String s, int radix)
                 throws NumberFormatException {
+        return parseUnsignedInt(s, radix, 0);
+    }
+
+    /**
+     * Extend upon parseUnsignedInt(String, int) by providing a start offset
+     * to enable parsing substrings without creating intermediary objects
+     * @see java.lang.Integer#parseUnsignedInt(String, int)
+     * @param start the start position in s to parse from, inclusive
+     */
+    static int parseUnsignedInt(CharSequence s, int radix, int start)
+            throws NumberFormatException {
         if (s == null)  {
             throw new NumberFormatException("null");
         }
+        return parseUnsignedInt(s, radix, start, s.length());
+    }
 
-        int len = s.length();
+    /**
+     * Extend upon parseUnsignedInt(String, int) by providing a start and end
+     * offset to enable parsing substrings without creating intermediary objects
+     * @see java.lang.Integer#parseUnsignedInt(String, int)
+     * @param start the start position in s to parse from, inclusive
+     * @param end the end position in s to parse to, exclusive
+     */
+    static int parseUnsignedInt(CharSequence s, int radix, int start, int end)
+            throws NumberFormatException {
+        if (s == null) {
+            throw new NumberFormatException("null");
+        }
+        int len = end - start;
         if (len > 0) {
-            char firstChar = s.charAt(0);
+            char firstChar = s.charAt(start);
             if (firstChar == '-') {
                 throw new
                     NumberFormatException(String.format("Illegal leading minus sign " +
                                                        "on unsigned string %s.", s));
             } else {
                 if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
                     (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
-                    return parseInt(s, radix);
+                    return parseInt(s, radix, start, end);
                 } else {
-                    long ell = Long.parseLong(s, radix);
+                    long ell = Long.parseLong(s, radix, start, end);
                     if ((ell & 0xffff_ffff_0000_0000L) == 0) {
                         return (int) ell;
                     } else {
                         throw new
                             NumberFormatException(String.format("String value %s exceeds " +
                                                                 "range of unsigned int.", s));
                     }
                 }
             }
         } else {
-            throw NumberFormatException.forInputString(s);
+            throw NumberFormatException.forInputString(s.toString());
         }
     }
 
     /**
      * Parses the string argument as an unsigned decimal integer. The